The present disclosure relates generally to wellbore operations and, more particularly, to an adjustable jar and accelerator system and methods of use thereof.
During the drilling and completion of wellbores in the oil and gas industry, objects such as drill pipe, collars, downhole tools and other apparatus can sometimes become stuck due to differential sticking, key seating, hole sloughing and other common wellbore conditions. In such situations the stuck object can oftentimes be freed through the application of ordinary tensile or compressive forces delivered from the surface. In other situations, however, the stuck object must be freed through the downhole delivery of sharp jarring forces.
Devices for delivering such jarring forces are typically known as jarring devices or “jars.” Jars generally include an outer housing which can locate and become attached to the stuck object. In particular, the housing generally contains a core rod or movable mandrel that can be coupled to a latch tool, or other attachment tools below the jar, which effectively couples the jar to the stuck object. The mandrel is telescopically connected within the housing, and the housing is attached to pipe, coiled tubing, wireline, slickline, or another type of conveyance extended from the surface. Typically contained within the jar is a force responsive latch means, which maintains the jar in a “set” position until a preselected axial force is exceeded, at which point the latch mechanism releases and thereby allows the jar to “stroke” and deliver a jarring impact to the stuck object.
Such jars may be utilized alone, or in cooperation with downhole devices that store or accumulate an increased amount of energy to be delivered to the stuck object. Such devices are typically referred to as accelerators, accumulators, jar boosters, or intensifiers. As used herein, the term “accelerator” will be used to refer to any of the foregoing. The accelerator device is typically arranged adjacent the jar in the tool string and its primary function is to store an increased amount of energy in response to upward or downward displacement of the work string, thereby enhancing the jarring impact on the stuck object when the jar strokes.
Before the accelerator and jar combinations are deployed downhole, a well operator is required to estimate or otherwise predict approximately how much impact force will be needed to free the stuck object. The operator then sets or otherwise configures the accelerator and jar combination to deliver the approximate impact force. Setting the required impact force at the surface can be a problem if the operation requires an alteration to the impact force once the tool is located downhole. Another problem with typical accelerators and jars that are currently used in the field is that they require line tension to activate. This becomes a problem in very deep wells where the over pull available from a slickline unit, for example, is limited due to line weight and line friction. Another major downfall of traditional jar and accelerator combinations is that they can inadvertently cause damage to sensitive components in a tool string by cyclical jarring past tool design limits.